Before Barack Obama was even elected he was called a "law breaker" by many Americans who didn't believe the Senator had met the basic requirement of being a natural born citizen.
It didn't end there. Immediately after being elected, elected officials of both parties challenged the constitutionality of the President's use of "Czars" rather than appointing individuals who had to face Senate approval, such as cabinet officials. Liberal Senator Robert Byrd (D-WV) wrote a scathing letter to the President, stating "As presidential assistants and advisers, these White House staffers are not accountable for their actions to the Congress, to cabinet officials and to virtually anyone but the president," Byrd wrote. "They rarely testify before congressional committees, and often shield the information and decision-making process behind the assertion of executive privilege. In too many instances, White House staff have been allowed to inhibit openness and transparency, and reduce accountability." Still, Byrd was an anomaly. The vast majority of his Democrat colleagues had no problem with Obama's "power grab."
Obama has also been criticized for his very selective enforcement of the law; yet Article 2, section 3 of the Constitution mandates that the laws be "faithfully executed." He has not enforced laws on immigration, did not defend the Defense of Marriage Act in courts, and even failed to fully enforce federal voting laws.
Obama has used executive orders to augment what he could not get pass into law. He implemented "cap & trade" provisions in the EPA bill that did not pass the US Senate. He made GM, a major US auto company, into a government entity, and even ordered a moratorium on off shore oil without Congressional approval (and continued it long after being mandated by the courts to discontinue such). This is just part of a long list of such autocratic measures.
The House Oversight Committee has probably never been more busy than during the Obama Administration. This includes the very turbulent Nixon years. Obama's administration is accused of failing to be truthful and failing to provide information to Congress on a plethora of major issues. This includes blocking Congress from getting documents about Fast and Furious and the death of Border Patrol Agent Brian Terry, a bizarre cover-up over the death of US officials in Benghazi (including the arguing that the attack was because of a movie that was clearly not the case), stonewalling on the efforts of Congress to investigate the IRS targeting of conservative organizations, etc.
Finally, progressives are attacking the Obama's violation of the law. International law, that is. The Daily Beast is reporting that "The White House has an answer for critics who want to know how the Obama administration can justify striking ISIS inside Syria under international law: If and when we actually do it, we will come up with a legal justification then."
Even his "domestic justification" for this attack of ISIS has critics among the more liberal news sources. Obama's justification is based on the argument that acts passed 13 and 12 years ago in 2001 (to go to war against Afghanistan) and 2002 (against Iraq) are applicable today. The New York Times has called such explanations "perplexing" and insufficient. (After all, al Qaeda and ISIS have fought with one another, and the Saddam regime is ancient history.)
But even if Obama's "domestic" argument is accurate, there are few in foreign policy circles (particularly among progressives) that can find justification for Obama making such an attack. In particular, the Administration's attacks would be a violation of international law of armed conflict and the United Nations charter. But the NSA is letting it be known that this concern will be addressed, "With respect to international law, the specific basis will depend on the particular facts and circumstances related to any specific military actions, but we believe that we will have a basis for taking action", says spokesperson Caitlin Hayden. They have no idea what legal justification they have at this point, but they will figure it out when they deem necessary.
Many conservatives have complained about Obama's "lawlessness" for years and now many on the left are concerned about the Administration's disregard of the law. For the former, it is the US Constitution, and the latter, the innocuous "international law." In the end, I think both sides can expect Obama to continue his policies of "business as usual" and do so without serious consequence. There is not enough courage on any side to hold him accountable.