I understand the point raised by the thread starter, but in my humble opinion, the question should have been "Is it a crime to engage in s3xual intercourse inside a private vehicle?" The terms "legal" and "illegal" seems confusing but we know the thread starter's intention. No punt intended.
As far as I'm concerned, there is no specific law punishing s3xual activities inside a private vehicle. What we have is Article 200 under the
Revised Penal Code defining the crime of grave scandal. However, most defense lawyers would argue the terms used in the definition. Say, the word "decency" is highly subjective—what may be decent for you may not be decent for me, vice-versa. Lawyers are paid to protect their clients and uphold the law or question its legality.
Sa makalusot lang.