Legislation is 'passed'; executive edicts are 'declared'. Some would argue that such declarations are irrelevant if unconstitutional and can be ignored; regardless, executive actions only direct those under executive branch & the judiciary & legislature can ignore and or oppose them them.
Anything Obama declares today can be undeclared tomorrow just as quickly by next President.
Sure, any executive action could be reversed by the next president but there is no guarantee of that happening. Also, imagine the damage that would be done between now and then even if the next President did reverse it. How would that damage be undone? Could it be undone? Could we ever recover from the damage?