"Have" vs. "Is" + Verb

It often happens in English that, in a particular lexical or syntactic environment, two or more constructions that resemble one another somewhat become synonymous, for whatever reason, and get harder to distinguish in that context.

Constructions are habits, and different people form them differently, and with different usages; and if they only notice them in certain contexts -- like in writing, or in a legal announcement like the ones in the question -- they may well associate them only with that context. And so language changes.

In this case, Ryan is correct that is expired is a 3SgPres predicate adjective construction, while has expired (use has, not have; it's not parallel to is and functions as a red herring for the reader) is a perfect construction.

And in this case, if it has expired (Vb PPpl), then it is expired (Adj), just from what expire means and the Stative/Resultative sense of the perfect. So they're synonymous. Here.

Not everywhere.

For one instance, you can expand just about any predicate adjective into an attributive adjective for its subject, but you can't do that with a perfect participle:

• That ticket is expired. ~ That is an expired ticket.
• That ticket has expired. ~ **That has an expired ticket.* (grammatical, but unrelated)

For another, you can modify real verbs with clauses that don't play well with predicate adjectives:

• That ticket has expired since Tuesday/since I last checked it.
• **That ticket is expired since Tuesday/since I last checked it.*

There isn't all that much difference between the two semantically, though the grammatical differences have already been mentioned.

Insofar as there is a difference it is this: "has expired" has the emphasis on the process of expiration, whereas "is expired" has the emphasis on the present state.

For example, were one to buy a Norwegian Blue parrot, and it expired, what with all the pining for the fiords and all; one's compliant to the shopkeeper might be:

This parrot has expired!!

or

This parrot is expired!!!

In the first case there is an implication that it transitioned from dancing a Norwegian jig, to pushing up the daisies between the time of purchase and the present. This is not absolutely explicit, but is a subtle implication from the context.

The second is more of a statement, making no implication as the the state at time of purchase.

This is a bit of a stretch, in most cases they are synonymous, but insofar as there is a difference, this is it.

I view each of these sentences with slightly different meanings. These explanations are based on my personal experience.

"The milk has expired" is when you have already bought the milk and it expired in your refrigerator.

"The milk is expired" is when you are looking at the expiration date before you buy it and realize it is in fact expired.