People use intellectual property laws to extort money. If I create something and try to sell it, I find that there are people who have patents with no intention of creating a product. They just wait for someone to create something similar to the patent, and then use the patent to extort money.
This isn't state law but federal law. Note toward bottom a owner of a private home can deny service dog on their property. Not sure why you would deny a friend but you are within your legal rights to deny at home. Add - makes more sense since you have allergies & one of the reasons why it is up to the individual owner to chose whether or not to allow a service dog. Just ask friend not to bring dog over due to your allergies.
Though service animals of all kinds can legally accompany their disabled handler almost anywhere the handler goes, they can be excluded from areas where their presence would constitute either a fundamental alteration of goods and services available for all or a direct threat to safety. Examples where a service animal might be excluded include:
-Sterile rooms, such as operating rooms, some areas of emergency rooms/departments, some ICU rooms, some ambulances, some delivery rooms (on a case-by-case basis)
-Clean rooms where microchips are manufactured
-Places where food is prepared (though they cannot generally be excluded from dining areas where food is present) (by order of most health departments)
-Open air zoological exhibits, such as open air aviaries (at the zoo's discretion)
-Churches (at the church's discretion)
-Native American Tribal Council Chambers (at the council's discretion)
-Federal Courts (at the judge's discretion)
-Jail or prison cells (at the discretion of the facility director)
-Private clubs (at the club's discretion)
-Private homes (at the home owner's discretion)
So far, this discussion is centered entirely on laws of access in the United States of America. Other countries will have their own laws in place regarding the access rights of individuals accompanied by a service animal.