Some languages have no grammar.
Grammar is: “the set of rules which the people of the language follow when they speak”
The conclusion is draw that every language has their grammar or otherwise no communication is possible or the language would be useless for communication. Language is compared to each other by looking at the grammar of English, Maori and Latin. Every language by definition must have a grammar. Thus, any language that claims to have no grammar is not a language.
Baur, L., & Trudgill, P. (1998). Language myth. In Baur, & Trudgill, Language myths. London: Penguin Books.