Is an external IRA rollover into TSP re-characterized for tax purposes?

Hello,
In Maryland, they are starting to NOT tax distributions from the TSP (total state tax free 401k/pension distributions via MD Retirement Tax Elimination Act), but WILL tax distributions from an IRA. If I move most of my money from the TSP to a fideility IRA (for better returns) and then, years later, move the fidelity ira back into the TSP, will I be able to withdraw the money from the TSP with the same Maryland tax free status? OR, are there any re-characterizations of the money that take place upon the TSP money since it once existed in the external IRA?