RDAP source
https://rdap.nic.cz
port 43: whois.nic.cz
The registry blocks transfers. Often set for valuable or disputed domains.
Signed delegation in place.
WHOIS source
whois.nic.cz
REG-WEBGLOBE REG-MOJEID REG-WEBGLOBE REG-WEBGLOBE REG-KRAXNET REG-KRAXNET
Webglobe, s.r.o. KRAXNET s.r.o.
Make a direct request at ICANN.