Jan Kalvoda resigned from his position because he had improperly used the title of JUDr.
A fight immediately broke out in the ODA for the post of the new party chair. Deputy Prime Minister and ODA chief Jan Kalvoda resigned from all his government posts yesterday. At the same time, the leadership of the alliance indicated that Kalvoda would also leave the party leadership. Last night in the Chamber of Deputies, Kalvoda said he is not a doctor of law and admitted that the unauthorised use of the title of JUDr. was a big mistake. He has already sent his resignation as justice minister to the president of the republic and given up his seat in parliament.
Source https://hn.cz/jan-kalvoda-rezignoval-na-sve-funkce-nebot-neopravnene-uzival-titul-judr