The DofI may be the best outline ever created to justify secession.
Prudence, indeed, will dictate that governments long established should not be changed for light and transient causes; and accordingly all experience hath shown that mankind are more disposed to suffer, while evils are sufferable, than to right themselves by abolishing the forms to which they are accustomed. - Declaration of Independence (DofI).
A state can't just up and say, "OK we’re outta here." Individuals may leave, but not a state. A state purporting to govern itself must have more than "transient causes" to overthrow that which governs it.
But when a long train of abuses and usurpations, pursuing invariably the same object evinces a design to reduce them under absolute despotism, it is their right, it is their duty, to throw off such government, and to provide new guards for their future security. - DofI.
Where is the "long train of abuses" CA has suffered? Where has CA gone on record to show how it has suffered "a long train" of unconstitutional federal acts of “despotism” or tyranny, the ONLY legal, moral, and prudent justification for secession?
+1
“California does not have the moral or legal justification to secede and I don’t think the federal government should allow it without some kind of compelling justification.”
Who would determine that California does, or does not, have a moral justification?
Would it be the people of California, or some independent second party - say, for example, the King of England?