That review concluded that there was no viable way of extending the act to offenders convicted before the legislation came into force, beyond the limited retrospection with respect to those serving relevant sentences on 1 September 1997.There are measures, however, to protect the public from sex offenders who have completed their sentences prior to 1997 but who continue to display risky behaviour. Chief constables can, for example, apply for a Sex Offender Order, which triggers notification and can place prohibitions on the individual.A number of changes to strengthen the existing sex offenders' regime are contained in the Sexual Offences Bill currently before the UK Parliament.