Today's Washington Examiner Editorial, "Czar Obama Takes Aim at Congress" is a great read on this issue:
There are so many deep flaws in the "Endangerment Ruling" announced Monday by President Obama's Environmental Protection Agency that it is quite possible the worst of them will escape notice. After all, it's hard to top the drama of the millions of lost jobs and the crippling energy crisis that will result if the agency begins regulating greenhouse gases -- mainly CO2. The agency unilaterally awarded itself authority to do just that with the ruling. But even worse will be the terrible damage this ruling will inflict upon one of the most basic of American constitutional pillars, the separation of powers among co-equal branches, in this case the president and Congress. Obama has launched a thermonuclear warhead aimed directly at the very heart of congressional authority.