Kurt Ullman wrote:

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Crimea is an autonomous parliamentary republic within Ukraine

It is a SEMI-autonomous area within the Ukraine.

Says what authoritative source?

Haven't seen anything that suggests they have control over such
things as inviting people to invade.

Not all rules, regulations or rights are specifically enumerated in a
constitution. Any american should know that.

Do you have the right to put cream in your coffee? Where is it written?