Since the introduction of the Inter Registrar Transfer Policy (IRTP) by ICANN a registrar is only allowed to refuse a domain name transfer under certain circumstances. Since the domain owner agrees to transfer his domain by giving his consent via email.
In order to exclude domain hijacking and other reasons for unintentional transfers, some registrars (for example Networksolutions) have converted their whole stock of gTLD to "Registrar LOCK".
This means that domains have to be unlocked at the registrar before transfer can be started (incoming or outgoing). After release of Registrar LOCK the status: ACTIVE is indicated in the WHOIS data set, and after that transfers can be started.
At Networksolutions this is, for example done via the domain account when “domain protect“ is set to “off”.