Large snakes and monitors sit at the point where pet keeping meets wildlife law, tenancy law, and insurance. None of those layers cares what the seller told you, and each one can end the keeping arrangement on its own. The work below is not about memorising anyone's law, because rules differ sharply between neighbouring areas. It is about checking your own position, in writing, before an animal depends on the answer.
Start with the wildlife authority and its species list
Find the government wildlife or animal-keeping authority for your state, province, or country, and look for its published list or schedule of species that may be kept, kept with a permit, or not kept at all. Search that list for the exact species you want, by its scientific name as well as its common name, because schedules are usually organised by scientific name and common names vary.
Read the conditions attached to the species, not only its presence on the list. Schedules often attach size thresholds, enclosure standards, source requirements, or a rule that the animal must come from a licensed breeder with documented provenance. If the list is unclear, contact the authority directly, describe the species and your address, and ask what applies to you. Keep the written reply with your records, because a dated answer from the authority is worth far more than a screenshot of a forum discussion.
Check the local layer separately
A species that is legal nationally can still be restricted locally. City and council rules sometimes set their own limits on large constrictors, venomous species, or reptiles above a certain length, and those rules are usually published in local animal-keeping or zoning ordinances. Search your council or city website for reptile, exotic animal, and animal-keeping terms, and if the published wording is ambiguous, ask the council the same direct question you asked the wildlife authority.
Check homeowners' association or building rules too, where they apply. A private rule cannot make an illegal animal legal, but it can make a legal animal a breach of your housing agreement, which is the same practical problem arriving by a different door.
Check your housing and insurance position
If you rent, read your tenancy agreement for pet and exotic animal clauses, and get your landlord's written agreement for the specific species before you buy, not a verbal nod to pets in general. A large snake or a monitor is exactly the kind of animal a general pets-allowed clause may not have contemplated, and discovering that after purchase puts the animal's home at risk.
Tell your household insurer what you plan to keep and ask whether the policy covers the animal, damage it could cause, and liability if it escapes or injures someone. Insurers treat large reptiles differently from cats and dogs, and an undisclosed animal can complicate a claim that has nothing to do with the animal itself. Get any confirmation in writing and keep it with the permit paperwork.
Verify the seller's paperwork as well as your own
Ask the seller for the animal's provenance: where it was bred or imported, what permit or licence the seller holds, and what documents will transfer with the animal. A seller who keeps lawful animals usually produces this readily. Walk away from a seller who urges you to buy first and sort the rules later, because an animal bought into the wrong jurisdiction may have to be surrendered, and that outcome falls on the animal rather than on the seller.
Once every layer checks out, file the permit, the authority's reply, the landlord's agreement, and the provenance papers together before the animal arrives. KinsLe's Pet Passport keeps that permit, provenance record, and keeper history in one organised packet, so the documents a large snake or monitor depends on are never scattered when an official asks for them.