Both the federal and California Constitutions contain provisions prohibiting ex post facto laws. (U.S. Const., art. I, 10; Cal. Const., art. I, 9.) Included within the ex post facto prohibition is any law that retroactively increases the punishment for a criminal act. ( Collins v. Youngblood (1990) 497 U.S. 37, 43 [110 S. Ct. 2715, 2719, 111 L. Ed. 2d 30, 39].) The ex post facto clause does not prohibit all increased burdens; it only prohibits more burdensome punishment. ( People v. McVickers (1992) 4 Cal. 4th 81, 84 [13 Cal. Rptr. 2d 850, 840 P.2d 955].) In People v. Castellanos (1999) 21 Cal. 4th 785, 795 [88 Cal. Rptr. 2d 346, 982 P.2d 211], the Supreme Court stated the test for a punishment for the purposes of the ex post facto clause. The test is, "whether the Legislature intended the provision to constitute punishment and, if not, whether the provision is so punitive in nature or effect that it must be found to constitute punishment despite the Legislature's contrary intent." In Castellanos the question was whether section 290, requiring sex offenders to register with the police, could be retroactively applied. The court stated that the purpose of the sex offender registration statute was to ensure that persons convicted of the crimes listed in the statute are readily available for police surveillance. This is because our Legislature has deemed them likely to commit similar offenses in the future. (People v. Castellanos, supra, 21 Cal. 4th at p. 796.) The court concluded that the statute did not constitute punishment and that its retroactive application did not violate the ex post facto clause.