They don't address whether it is a federal civil right to have one's electors appointed if they win.
I can't see how the Civil Rights Acts could be met with any other construction, but judges are nothing if not creative.
They will need 60 votes in the Senate and a majority in the House to put together a Compact. Case law is pretty clear that bridges are okie dokie but an increase in the states political power at the expense of the federales brings Article 1, Section 10 into play and Congress has to give the okie dokie.
Of course that post is totally dependent on the 'political' makeup of the SCOTUS when it gets litigated. :-}