The changes to the tax law beginning in the 2018 tax year have not affected the deduction for Public Safety Officers. The instructions for both federal and non-federal retired PSO's are below.
For federal PSO's, IRS Publication 721 instructions cover Distributions Used To Pay Insurance Premiums for Public Safety Officers. The current link is IRS Publication 721. The CSRS and FERS are specifically stated to be eligible retirement plans for federal PSO's.
For state and local PSO's, the instructions are contained in IRS Publication 575, Insurance Premiums For Retired Public Safety Officers. The link is IRS Publication 575
If you are claiming the PSO deduction and are itemizing your deductions, you should double check your return to be sure your PSO claimed insurance premiums are not claimed again under your medical expense deductions.