Yes, it's against the building code and also against the health and safety code.
Have you contacted the builder? If so, what was their response?
Have you contacted the building inspector?
Did you buy the house new?
It's against the building code NOT to install a trap in a bath tub. The necessity is to prevent sewer gases (all the gases that can potentially be in the sewer system and are in the sewer system) from entering the home by the use of standing water.
So, if you can testify that you did no repair work and there isn't a trap - then the builder must have failed to install such - a violation of the building code.
DISCLAIMER: Answers from Experts on JustAnswer are not substitutes for the advice of an attorney. JustAnswer is a public forum and questions and responses are not private or confidential or protected by the attorney-client privilege. The Expert above is not your attorney, and the response above is not legal advice. You should not read this response to propose specific action or address specific circumstances, but only to give you a sense of general principles of law that might affect the situation you describe. Application of these general principles to particular circumstances must be done by a lawyer who has spoken with you in confidence, learned all relevant information, and explored various options. Before acting on these general principles, you should hire a lawyer licensed to practice law in the jurisdiction to which your question pertains.
The responses above are from individual Experts, not JustAnswer. The site and services are provided “as is”. To view the verified credential of an Expert, click on the “Verified” symbol in the Expert’s profile. This site is not for emergency questions which should be directed immediately by telephone or in-person to qualified professionals. Please carefully read the Terms of Service (last updated February 8, 2012).