There are two cases for the question you have asked -

(1) Doing two courses simultaneously -

As per UGC Secretary Rajnish Jain , " A student will be allowed to pursue two degrees (courses) simultaneously but for both the degrees the mode of delivery will be different. A student pursuing a regular degree can pursue a second degree only via ODL (Online Distance Learning) or online mode. " (Source - Times of India, Date - May 22, 2020).

So as per the above statement, it is legal to do two courses simultaneously, provided you do one course via ODL.

(2) Doing two courses, one a fter the other -

You can also do this - complete a course and then do another course. It is very common among MBBS graduates who do LLB after completion of MBBS. It is legal to do two courses.