That's true, but whether someone has authority to show up at your door and ask questions about your sex life or whatever is purely based on church authority, not legal authority. I think it's important for readers to know that the elders have no legal authority to compel you to follow any church procedure, such as answering questions or attending judicial committees.
A common misconception that I have seen on this forum is that baptism is a legally significant event. If it were really some sort of contract, it would be invalid in the case of minors, which we all know it isn't. Minors can't enter binding contracts in the U.S. and other common law countries (and most civil law countries as well). The fact that it took place would be admissible if someone were to file a lawsuit seeking damages, but so would just about anything else of relevance.