The principal’s statement that you may not be able to enroll in the Bar Council with an open university certificate might be true, depending on specific rules and regulations set by the Bar Council of India (BCI). The **Bar Council of India** has strict guidelines regarding the eligibility of students enrolling in the LLB course and subsequently registering as advocates.

As per BCI rules, a candidate must have completed their 10+2 (or equivalent) from a recognized board or university, which must be recognized by the BCI for admission into law courses. While **open schooling** is accepted by many universities, certain open school certificates might not meet the BCI's recognition standards for enrollment as an advocate.

You should:

1. **Verify with the Bar Council**: Contact the Bar Council of Telangana or the Bar Council of India directly to get a clear answer on whether your specific open university board certificate is recognized for enrolling as an advocate after completing BA LLB.

2. **Check BCI Recognition**: Ensure that your open university certificate is from a board or institution recognized by the BCI.

If your open university is not recognized, you may face challenges in enrolling with the Bar Council, despite completing your law degree. Seek official confirmation to understand your options.