How is it unconstitutional to attach conditions to federal money? It is in fact done all the time. How is it unconstitutional to require States to comply with federal law to receive federal funding? This too is a long standing practice.
What kind of crackpot attorney are you? By your logic the federal government under every president has committed unconstitutional acts against the States. 
Again, it's not the executive order that is the problem, it's who issued it.