February 05, 2011 
Some  conservatives, including AT news editor Ed Lasky, are worried that  despite the election of a Republican-dominated House and six new GOP  senators, Obama will continue to advance his extremely liberal agenda --  but this time, by executive fiat rather than by congressional law.
 
He has already received his marching orders from the Center for American Progress (CAP) -- called his "Ideas Factory" by TIME and his "Policy Font" by Bloomberg News. After the shellacking, the CAP released a report calling for Obama to rely on increased use of executive powers to push his agenda (and ignore the wishes of the American people and the role of the newly constituted Congress): "Executive orders, Rulemaking, Agency management, Convening and creating public-private partnerships, Commanding the armed forces, Diplomacy."
[L]ike all presidents, he has a bulging toolkit: executive orders, regulations, spending decisions, the bully pulpit and more. Obama has lots of power, and he should wield it[.] ...
Consider energy policy, where congressional gridlock seems inevitable, with many conservatives insisting climate change is a myth and taxes are a nightmare. The Center's experts say Obama could impose a $2-per-barrel fee on imported oil with proceeds steered toward energy research.
Essentially,  the CAP has claimed that Obama is an omnipotent king who can issue any  edict he wants to on any thematic issue.  The good news for America and  its people is that the CAP is flat wrong.
Obama  is not an omnipotent dictator, and he doesn't even have a "bulging  toolkit."  Like all of his predecessors, he is a president with only  limited prerogatives, according to the U.S. Constitution.  And it is the Constitution, not Obama or the CAP, that determines what a U.S. president is allowed to do.
Obama has no prerogatives except those explicitly granted to him by the Constitution (specifically, by its Article II).
As explained (inter alia) in this constitutional primer,  the prerogatives of the entire federal government are thematically  limited to a discrete group of thematic issues.  On top of that limit,  the President of the United States is limited in terms of what he can do  about them. 
So what about that "bulging toolkit"?
Executive  orders and regulations issued by the president are law for no one  except federal executive agencies.  Only the Congress can make law for  anyone else.  So any executive orders or regulations are not law for you  unless you work for one of these institutions.  The same applies to any  executive regulations imposed by executive agencies such as the EPA.
Fees on imported products?  Again, only the Congress can impose them.  The exclusive prerogative to impose any duties, taxes,  or imposts is reserved by the Constitution for the Congress.  And under  the nondelegation doctrine, one branch of the federal government cannot  delegate its prerogatives to another.
Spending  decisions?  Again, they are for only the Congress to make.  The  president can only request budgets, and if he deems whatever  appropriations the Congress enacts insufficient or excessive, he can  only veto them entirely (not partially -- he does not have a line-item  veto right, which the SCOTUS declared unconstitutional).
What about the president's prerogatives as commander of the U.S. military?  The answer can be found in the Constitution and in Federalist #69:
The President is to be commander-in-chief of the army and navy of the United States. In this respect his authority would be nominally the same with that of the king of Great Britain, but in substance much inferior to it. It would amount to nothing more than the supreme command and direction of the military and naval forces, as first General and admiral of the Confederacy, while that of the British king extends to the declaring of war and to the raising and regulating of fleets and armies -- all which, by the Constitution under consideration, would appertain to the legislature.
The  president is the supreme commander of the military, but he doesn't  decide military spending levels, the Armed Services' size, or which  countries the U.S. wages war with.  As James Madison clearly stated,  you're not allowed to go to war without a declaration of war -- and that  is the Congress's prerogative.
The Executive Branch can't even unilaterally retire certain categories of ships and aircraft.  It has been forbidden to do so by the Congress.
Article 1, Sec. 9 of the Constitution says that "[n]o money  shall be drawn from the Treasury, but in Consequence of Appropriations  made by law."  Obama cannot determine spending levels unilaterally.  And  if he vetoes Republican-proposed spending reductions...fine.  The  government will receive no funding, then, which means that Obama will  get no budget at all instead of a small budget.
Moreover,  according to the Constitution, the Congress has the prerogative to 1)  raise and support armies; 2) provide and maintain a navy; 3) provide for  the "common defense"; 4) make regulations for the military (such as the  former DADT law); and 5) to "define and punish ... [o]ffences against  the Law of Nations."  In other words, the Congress regulates the  military and makes law for the Executive Branch, and the latter obeys  that law.  And not only does the president swear an oath to support the  Constitution, but he also is commanded by it to "take care that laws be  faithfully enacted."
The  president cannot convene public-private partnerships, because the  Constitution doesn't list any such presidential prerogative.
Nor can he use the U.S. military against the American people -- the Posse Comitatus Act prohibits him to do so.
As  for diplomacy, this can be used only towards foreign countries, again  within limits set by the Constitution and the Congress.  The president  cannot unilaterally appoint anyone to crucial offices without Senate  confirmation, nor can he ratify treaties without the Senate's consent.   Nor can the Senate ratify any treaty it likes -- it can ratify only  treaties that are authorized by the Constitution.  It cannot okay a CO2-emissions-limiting accord, because the Congress and the president have no constitutional right to regulate CO2 emissions.
Moreover,  the Congress has the right to supervise the president as he manages  America's foreign policy.  It can, for example, order a U.S. embassy to  be relocated, order (or prohibit) the Executive Branch from doing  something, and demand testimonies by Obama administration officials  before CSPAN.  The Congress can limit Obama's foreign policy in many  ways.
To  sum up, Obama will make a serious mistake if he tries to advance his  liberal agenda by executive fiat.  He has no constitutional prerogative  to do so.  With the exception of employees of federal agencies and the companies that do business  with them, Americans will not be bound by any edicts Obama might  issue.  Meanwhile, the Executive Branch will be bound by any laws the  Congress might make -- and of course, it is already bound by any acts  already passed by the Congress to date.