Squid is http proxy so it can not proxy http secure requests even if it is not in transparent mode. But you can deny https sites by denying connections that use CONNECT method or use port 443 acl to block the connections on the port.
like:
Code:
acl connect method CONNECT
acl https_port port 443
.
.
.
.
http_access deny connect
http_access deny https_port
{
all other access rules here
}
