There is nothing liberal about setting aside constitutional law.    The ends justify the means is not liberal either.    

Lincoln is the only president faced with secession, no constitutional guidance or process to handle that situation.   His objective was to keep the union intact  and he was unwilling to concede to continued institutional slavery.    Blame that on him if you like, or, blame it on the south for not dropping slavery.  Either way the war was fought, the South lost, we have a single nation.  

Maybe we can watch Spain and the Catalonia situation - they have already suspended what some consider 'the law' of Spain.