In a release today, Dr Reti said the law allows clinicians to ask about symptoms, take temperatures, listen to the chest and take swabs.
He said it was worrying to hear that other examinations including blood tests and pulse recordings were also happening, and consent was only being requested for swab tests.
"National supports mandatory coronavirus testing in isolation, but it is important care is taken to make sure no one is being subjected to unlawful examinations," Dr Reti said.
"[Health Minister Chris Hipkins] claimed in Parliament that people are consented for medical procedures while in isolation. But written questions show that consent is only being requested for swab tests," he said.
"Isolation is a captive environment with altered autonomy, so great care must be taken with medical examinations beyond what the legislation allows."
However, a Ministry of Health spokesperson said there was no suggestion that people in isolation were being subjected to illegal medical tests.
They said that although the law specified tests that must be done for COVID-19, it was up to doctors what other tests they ordered, and usual consent processes would apply in those cases.
"All medical tests or procedures at facilities are carried out by health professionals and all health professionals are governed by a code of practice under which all patients must be informed of any risks and benefits and under which all patients have a right to refuse testing," the spokesperson said.
"Caring for the health of those staying at facilities is an important aspect of ensuring the well-being of those returning to our shores while they are staying in these facilities and it would be remiss not to pay attention to other health needs beyond COVID-19 alone.
"As a result, we're committed to, where possible, providing holistic health care to those in these facilities. Any medical procedure or test requires informed consent and this includes those taking place in managed isolation and quarantine facilities."
The spokesperson said consent was normally obtained orally.
"Informed consent is only required to be in writing if: a) the consumer is to participate in any research; or b) the procedure is experimental; or c) the consumer will be under general anaesthetic; or d) there is a significant risk of adverse effects on the consumer."